The present invention relates to a magnetic circuit with a coil, and a method of making such a circuit.
Magnetic circuits with coils are used in many fields including those relating to current sensors and transformers. In applications such as current sensors, measurement precision is closely related to the magnetic properties of the materials used and to the manufacturing precision. Attaining a specified precision is often in conflict with the need to reduce manufacturing costs and the size of components.
A method of manufacturing a coil on a tore-shaped magnetic circuit is described in European patent EP 668 596. The method described in this patent, which attempts to respond to the above mentioned criteria, comprises the steps of winding a conducting wire coated with a thermo-adhesive around a cylindrical mandrel to form a coil, opening a magnetic circuit by separating ends thereof forming the air-gap, sliding the coil onto the magnetic circuit and subsequently closing the magnetic circuit.
This conventional method has a number of disadvantages. Firstly, it is very difficult to remove the coil from the cylindrical mandrel and thereafter insert it on the core. Secondly, opening and closing the magnetic circuit, as in any plastic deformation, deteriorates the magnetic properties of the circuit.